The present invention relates to an image forming apparatus and image forming method used in various types of devices such as a printer having a multi-value engine, facsimile equipment, an optical filing device, or an electronic sorting device, and more specifically to an image forming apparatus for selectively executing smoothing for inputted image data.
Conventionally some types of image forming apparatus such as a digital copier having multiple functions such as a facsimile or a printer have a multi-value engine section and a frame memory capable of storing multi-value data therein and output any of 1-bit/dot, 2-bit/dot or 8-bit/dot image according to the option.
FIG. 3 is a block diagram showing configuration of an image processing section based on the conventional technology for executing smoothing by converting binary image data to multi-valued image data. In this figure, a line buffer 301 is a memory for storing therein inputted binary image data for a plurality of lines and transfers a group of n(dot)xc3x97m(line) data around a remarked pixel to a template matching section 302.
The template matching section 302 compares the data group to a preset data group and transfers a result of comparison to a smoothing section 303. The smoothing section 303 converts a remarked pixel to a j(dot)xc3x97k(line) enlarged image for smoothing according to a result of comparison in the template matching section 302, while a dividing/smoothing section 304 executes the processing for dividing and smoothing the image according to an expansion ratio of the image and outputs the image data having been subjected to the processing for smoothing by converting binary image data to multi-valued image data.
In the image processing apparatus described above, to accommodate multi-valued image data, there has been known the apparatus in which a line buffer 401 for storing therein multi-valued data for a plurality of lines and a multi-valued template matching section 402 are provided, and smoothing processing for multi-valued image data is executed in the smoothing section 403 with the processing for dividing and smoothing executed in the dividing/smoothing section 404 as shown, for instance, in FIG. 4.
However, there occurs the problem that a larger memory capacity for an increased bit number for multi-valued image data is required for the line buffer section 401 as well as for the template matching 402. To solve this problem, a multi-value smoothing section 500 for multi-valued image data as shown in FIG. 5 is provided.
Even in a case of multi-valued image data for a remarkably jagged image, a density may be full (100%) in some sections, and to respond to this problem, a determining block 501 for determining whether density of an inputted multi-valued image is full or not is provided on the upstream side of a line buffer 502. It should be noted that a template matching section 503, a smoothing section 504, and a dividing/smoothing section 505 are provided, as described above, on the downstream side of the line buffer 502 and further a selector 506 is provided for switching the pixels to be converted according to a result of processing in the template matching section 503.
The determining block 501 supplies, for instance, only image data for pixels having a full density value of the image as shown in FIG. 6A as true value (1) to the line buffer 502, subjects the pixels to smoothing processing by converting binary data to multi-values in the template matching section 503, smoothing section 504, and dividing/smoothing section 505, and switching only the converted pixels with the selector 506.
Japanese Patent Laid-Open Publication No. HEI 9-130628 discloses as a technology related to the multi-value smoothing processing for the multi-valued image data for a color image as described above.
In the apparatus for processing multi-valued data based on the conventional technology as shown in FIG. 5, however, there are jagged images for characters and strings, so that it is not appropriate to execute smoothing processing only to 1-bit/dot binary image data. Therefore, it is required to execute smoothing processing to multi-value data. However, if input image data is subjected as it is to the smoothing processing there is a disadvantage that a larger memory capacity is required.
When a color image based on multi-valued image data is outputted, an image with a photograph (image section) and characters (character section) coexisting therein is required to be frequently outputted. Although the smoothing processing is effective for reducing jags in the characters, when the same smoothing processing is executed to the whole image to be outputted, if a data array identical to the template data is present also in any image section, the gradation becomes lower as the same processing is executed to both the character sections and image sections, which may sometimes generate a false contour not present in the original data thereof. Further, it is required in some types of data to execute smoothing processing only to black characters or to change the degree of the smoothing processing according to colors, but the conventional technology can not be applied to the cases as described above.
It is a first object of the present invention to reduce a data volume in template matching for the purpose to reduce a required memory capacity by converting multi-valued input image data to binary image data in a smoothing process.
It is a second object of the present invention to realize an optimal smoothing process by determining whether smoothing is to be executed or not according to the type of image data.
In the image forming apparatus according to the present invention, input image data is compared with a threshold value data previously set and is then converted to binary data, so that the amount of image data for a nxc3x97m area for comparison during template matching can be reduced.
Other objects and features of this invention will become apparent from the following description with reference to the accompanying drawings.